Flexible disk cassette with improved radial shift limitation structure for use in a magnetic recording and/or reproducing apparatus

ABSTRACT

A flexible magnetic disk cassette includes a flexible magnetic disk. A center core disk is also provided having a center hollow and raised fringe, and is attached at a center of the flexible magnetic disk with the raised fringe. A cover having an upper half and lower half for containing the flexible magnetic disk with the center core disk is provided. The lower half of the cover has a driving hole a little larger than an outer diameter of the center hollow of the center core disk.

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates to a flexible magnetic disk cassette capable ofbeing used for the recording and reproducing of various analog anddigital signals, and a recording and/or reproducing apparatus for theflexible magnetic disk cassette. More particularly, this invention isconcerned with a disk cassette having a cassette cover in which isrotatably accommodated a recording and reproducing disk havingflexibility such as a sheet-like magnetic disk (magnetic sheet), and arecording and/or reproducing apparatus for the same.

Description of the Prior Art

Referring to FIG. 1, there is shown a conventional recording andreproducing disk cassette designated by the reference numeral 1, whichcomprises a flat cassette cover 4 in the form of a rectangularparallelepiped composed of upper and lower halves 2 and 3, and asheet-like flexible magnetic disk (magnetic sheet) 5 accommodatedrotatably within the cassette cover 4. The magnetic disk 5 has amagnetic layer formed on both surfaces thereof, and on the central partthereof there is a center core disk 6 consisting of a circular platestuck thereon with adhesive or the like. In the central part of thecenter core disk 6 there is formed a rotary shaft insertion opening 7.

When the disk cassette 1 is installed (loaded) onto a magnetic recordingand/or producing apparatus (not shown), a rotating carriage 8 engages ina center opening 3a of the lower half 3 and at the same time a rotaryshaft 9 is inserted in the rotary shaft insertion opening 7. In thisstate the center core disk 6 is attracted and fixed onto the rotatingcarriage 9 by means of an attracting member (not shown) consisting of amagnet. In this case, the magnetic disk 5 is disposed centrally in itsthickness direction in consideration of the construction and dimensionof the cassette cover 4. On the other hand, the magnetic head 11 isinserted into a head insertion opening 10 formed in the lower half 3 andthen is brought into contact with the magnetic surface of the magneticdisk 5.

In such a loaded state, the center core disk 6 is rotated together withthe rotating carriage 9 by means of a driving unit such as a motor 12,whereupon the magnetic disk 5 is rotated within the disk cassette 1. Inassociation therewith the magnetic head 11 is moved in a radialdirection of the magnetic sheet 5 (namely in the direction of arrow inFIG. 27), thereby performing a desired recording or reproducingoperation.

In the disk cassette 1 of this sort, in order to prevent the peripheraledge portion of the magnetic disk 5 from striking against and being bentby the upper and lower halves 2 and 3, a ring-like projection 13 isformed on the inner surface of the upper half 2 to restrict thedisplacement of the center core disk 6 relative to the cassette cover 4.The disk cassette is installed, for example, in the followingdimensional relation relative to the cassette cover 4, the projection13, the center core disk 6 and the magnetic disk 5. The thickness l₁ ofthe cassette cover 4 is 3.4 mm; the plate thickness l₂ of the upper half2 is 0.8 mm; the plate thickness l₃ of the center opening portion 3a ofthe lower half 3 is 1.3 mm; the projecting length l₄ of the projection13 is 0.5 mm; the spacing l₅ between the magnetic disk 5 and theprojection 13 and the spacing l₅ between the magnetic disk 5 and aring-like projection 14 of the lower half 3 are each 0.4 mm; thethickness l₆ of the center core disk 6 is 0.5 mm; and the spacing l₇between the inner surface of the upper half 2 and the center core disk 6is 0.4 mm (see FIG. 2). Thus, the magnetic disk 5 is disposed centrallyin the thickness direction of the cassette cover 4.

However, when the disk cassette 1 is not installed on a magneticrecording and/or reproducing apparatus, that is when the disk cassette 1is not in use, if the magnetic disk 5 and the center core disk 6 movetoward the lower half 3 by virtue of their own weight as indicated witha dot-dash line in FIG. 2, there is formed a gap of about 0.3 mm betweenthe tip end of the projection 13 of the upper half 2 and the uppersurface of the center core disk 6. In the presence of this gap, themovement of the center core disk 6 is no longer restricted by theprojection 13, that is the center core disk 6 and the magnetic disk 5move freely in the horizontal direction within the cassette cover 4, sothat the peripheral edge portion of the magnetic disk 5 may strikeagainst the side of the cassette cover 4 and be bent thereby. Once theperipheral edge portion of the magnetic disk 5 is bent, it is no longerpossible to perform a good recording and reproducing operation in thevicinity of the bent peripheral edge portion.

Such an inconvenience is overcome by making larger thickness l₅ of thecenter core disk 6 and thereby making larger the overlapping length l₈between the projection 13 and the center core disk 6 at the time ofinstalling of the disk cassette 1. But this has not been realizedbecause of the resulting very narrowed space (particularly in thethickness direction) within the cassette cover 4 and because of, aspreviously noted, the requirement that the magnetic disk 5 must bedisposed centrally in the thickness direction of the cassette cover 4.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a flexible magneticdisk cassette which overcomes the foregoing problems associated with theprior art.

More specifically, it is an object of the present invention to provide aflexible magnetic disk cassette in which, even while the disk cassetteis not in use, the movement of the center core disk and hence of themagnetic disk are surely restricted within a predetermined range.

It is another object of the present invention to provide a flexiblemagnetic disk cassette which has a relatively flat shape.

In accordance with an aspect of the present invention, a flexiblemagnetic disk cassette includes a flexible magnetic disk, a center coredisk having a center hollow and raised fringe, and being attached at acenter of said flexible magnetic disk with said raised fringe. A coveris provided having an upper half and a lower half for containing thesaid flexible magnetic disk with said center core disk, said lower halfhaving a driving hole a little larger than an outer diameter of saidcenter hollow of said center core disk.

Other objects, features and advantages according to the presentinvention will become apparent from the following detailed descriptionof an illustrative embodiment shown in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view schematically illustrating aconventional disk cassette which is installed on the magnetic recordingand/or reproducing apparatus;

FIG. 2 is an enlarged sectional view taken on line II--II of FIG. 1;

FIG. 3 is an exploded perspective view of a flexible disk cassetteaccording to the embodiment of this invention;

FIG. 4 is a perspective view of an upper half of a cassette cover viewedfrom below;

FIG. 5 is a plan view of a center core disk viewed from a recessed sidethereof;

FIG. 6 is a perspective view of the disk cassette from below;

FIG. 7 is a longitudinal sectional view of a main part of the diskcassette showing its central portion, partly omitted;

FIG. 8 is a longitudinal sectional view of a main part of the diskcassette showing a guide means comprising a guide groove formed in thecassette cover and a pawl-like projection formed on a shutter;

FIG. 9 and FIG. 10 are each longitudinal sectional views of a main partof the disk cassette showing a modification of the guide means;

FIG. 11 is a longitudinal sectional view of a main part of the diskcassette showing an erroneous erase preventing detent formed on thecassette cover;

FIG. 12 is an exploded perspective view showing the disk cassette and amain part of a recording and/or reproducing apparatus according to theembodiment of this invention, onto which is to be installed the diskcassette;

FIG. 13 is a plan view of the above apparatus with a cassette pressuremember removed;

FIG. 14 is a plan view of the apparatus with the cassette pressuremember;

FIG. 15 is a sectional view taken on line XV--XV of FIG. 14;

FIG. 16 is a sectional view taken on line XVI-XVI of FIG. 14;

FIG. 17 is a sectional view taken on line XVII--XVII of FIG. 14;

FIG. 18 is an exploded perspective view showing a mounting state of arotor of a motor, a spacer, a leaf spring to which is attached aspring-biased driving pin, a yoke, and a motor cover;

FIG. 19 is a sectional view taken on line XIX--XIX of FIG. 13;

FIG. 20 and FIG. 21 are sectional views similar to FIG. 19 illustratingthe operation of the spring-biased driving pin;

FIG. 22 is an exploded perspective view of a main part of a head movingmechanism;

FIG. 23 is a perspective view of a rotational position detectingmechanism for the motor shaft of a step motor;

FIG. 24 is a sectional view taken on line XXIV-XXIV of FIG. 22;

FIG. 25 is a sectional view taken on line XXV--XXV of FIG. 24;

FIG. 26 is a longitudinal sectional view of a main part illustrating acorrelative operation between the erroneous erase preventing detent ofthe disk cassette and an erroneous erase preventing detent detectionmember;

FIG. 27 is a schematic side view illustrating the principle of acorrecting operation against an inward warp of upper and lower plates ofthe cassette cover; and

FIG. 28 is a plan view of the center core disk in a positioned statewith the motor shaft and a spring-biased driving pin respectivelyinserted in the motor shaft insertion opening and the spring-biaseddriving pin insertion opening both formed on the center core disk.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of this invention will be described with reference toFIGS. 3 to 28.

In this embodiment, a flexible magnetic disk cassette containing asheet-like flexible magnetic disk is installed onto a recording and/orreproducing apparatus and the recording and/or reproducing operation isperformed.

First, an explanation is here given concerning a disk cassette 26comprising a flexible magnetic disk 21 and a cassette cover 22. A shownin FIG. 3, the flexible magnetic disk 21 is formed of, for example, athin disk-like high polymer film having a thickness of 0.4 mm, and amagnetic layer uniformly formed on both surfaces to which arecording/reproducing magnetic head is to be brought into contact. Atthe center of the flexible magnetic disk 21 there is formed a circularcenter opening 21a (See FIG. 7) at which there is attached a center coredisk 23 made of a ferromagnetic material such as iron. The center coredisk 23 is formed from a flat disk by pressure and, as shown in FIG. 3and FIG. 7, on one side thereof there is formed a center hollow 23a, andon the other side thereof there is formed a disk-like convex portion23b. At the peripheral edge portion of the center core disk 23, there isformed a ring-like raised fringe 23c. Thus, the center core disk 3 isconstructed in the form of a pan. As shown in FIG. 7, a ring-like raiseddouble-sided adhesive sheet 27 is bonded to the raised fringe 23c of thecenter core disk 23, and the peripheral edge portion of the centeropening 21a of the magnetic disk 21 is bonded to the double-sidedadhesive sheet 27, whereby the center core disk 23 and the flexiblemagnetic disk 21 are joined together integrally.

At a nearly central part of the center cord disk 3, a square centeraperture 24 having a V-shaped corner is formed as a motor shaftinsertion aperture, and at a position which is distant by apredetermined distance from the center aperture 24, a rectangulardriving and positioning aperture 25 is formed as a positioning pininsertion aperture. As clearly shown in FIG. 5, the center 0₁ of thecenter aperture 24 is off the center 0₂ of the center core disk 23 andthe flexible magnetic disk 21, and is slightly distant by apredetermined distance toward the driving and positioning aperture 25.The center aperture 24 and the driving and positioning aperture 25 areformed so that a pair of diagonal lines d₁ and d₂ of the center aperture24 are each parallel with short and long side portions 25b and 25a ofthe driving and positioning aperture 25, respectively. Furthermore, thelength of one side of the center aperture 24 is slightly larger than thediameter of the motor shaft so that the motor shaft when fitted in thecenter aperture 24 provides a slight looseness. The reason why thecenter of the center aperture 24 is apart from the center of the centercore disk 23, as will be described in detail later, is that it isintended to coincide the center of the motor shaft fitted in the centeraperture 24 of the center core disk 23 with the center of the flexiblemagnetic disk 21 when the disk cassette 26 is installed onto therecording and/or reproducing apparatus.

On the other hand, the cassette cover 22 for accommodating the flexiblemagnetic disk 21, as shown in FIG. 3, is composed of an upper half 22aand a lower half 22b which are made of, for example, an injection moldedarticle from ABS resin containing an antistatic agent. The outerperipheral portions of the upper and lower halves 22a and 22b are weldedto each other to form a flat rectangular parallelepiped as a whole. At anearly central part of lower half 22b there is formed a circular centeropening as a driving hole 28, and at the peripheral edge portion of thedriving hole 28 and on the inner surface of the lower half 22b there isintegrally formed a ring-like projection 29. As shown in FIG. 6, theconvexed portion 23b of the center core disk 23 is fitted in the drivinghole 28 in a state which is slightly loose. On the inner surface of thecentral part of the upper half 22a, as shown in FIG. 4 there isintegrally formed a ring-like projection 30, and also around theprojection 30 there is integrally formed a ring-like projection 31 whichis concentric with the projection 30. The projecting length of theprojection 30 is longer than that of the projection 31 and hence, asshown in FIG. 7, the projection 30 extends beyond the projection 31 andprojects on the inner surface side of the lower half 22b. The ring-likeprojection 30 is inserted in the center hollow 23a of the center coredisk 23 in a state which is slightly loose.

Now, the cassette case 22, the upper and lower halves 22a and 22b, thecenter core disk 23, and the ring-like projection 30 of the upper half22a are, for example, in the following dimensional relation. Thethickness L₁ of the cassette case 22 is 3.4 mm, the thickness L₂ of anupper plate 22c and that of a lower plate 22d of the upper and lowerhalves 22a and 22b are each 0.8 mm respectively, the thickness L₃ of theupper plate 22c of the upper half 22a of the portion surrounded with theprojection 10 is 1.0 mm, the projection length L₄ of the projection 30is 1.5 mm, the thickness L₅ of the center core disk 35 is 0.3 mm, thethickness L₆ of the lower plate 22d of the lower half 22b adjacent tothe center opening 28 is 1.3 mm, and the height L₇ of the center coredisk 23 is 1.8 mm (See FIG. 7).

When the disk cassette 26 is installed onto the recording and/orreproducing apparatus as will be described later, the flexible magneticdisk 1 is disposed nearly centrally in the direction of the thickness ofthe cassette cover 22 as shown by the solid line in FIG. 7 and then isrotated. In this case, the distance L₈ between the fringe 23c of thecenter core disk 23 and the inner surface of the upper half 22a and thedistance L₉ between the flexible magnetic disk 21 and the projection 29of the lower half 22b are each 0.4 mm. The distance L₁₀ between the tipend of the projection 30 of the upper half 22a and a lower surface 23dof the center disk is 0.4 mm, and the distance L₁₁ between the outersurface of the lower half 22b and the lower surface 23d of the centercore disk 33 is 0.2 mm (See FIG. 7). When the disk cassette is not inuse, the center core disk 33 and the flexible magnetic disk 21 areplaced on the lower half 22b by virtue of their own weights, forexample, as shown by dot-dash line in FIG. 7. In this case, the tip endportion of the projection 30 of the upper half 22a and the projection 29of the lower half 22b overlap with each other by 0.4 mm (distance L₁₂)so even if the center core disk 23 is moved, a part of the center hollow23a of the center core disk 23 is sure to engage the projection 30.Thereby the looseness in a planar direction of the center core disk 23and hence the flexible magnetic disk 21 is kept within a predeterminedrange, and therefore the projection 30 and the center hollow 23a of thecenter core disk 23 are not disengaged from each other along with thedisplacement of the center core disk 23. In case the disk cassette 26 isturned upside down from the state shown in FIG. 7 and consequently thecenter core disk 23 is placed on the upper half 22a by virtue of its ownweight, the projection 30 comes into a completely fitted state withinthe center hollow 23a of the center core disk 23, so that, as in theaforesaid case, the amount of displacement of the center core disk 23and hence of the magnetic disk 21 is kept within a predetermined range.

In the disk cassette 26 having the above construction, the amount ofdisplacement of the center core disk 21 and of the flexible magneticdisk 21 can be regulated exactly by the projection 30 until a gapbetween the upper and lower plates 22c and 22d becomes wider by 2.2 mm(the sum of the overlapping length of 0.4 mm and the center core diskheight os 1.8 mm) while the upper and lower halves 22a and 22b are movedfrom the state shown in FIG. 5 toward the exterior, namely in thedirection in which the upper plate 22c and the lower plate 22d go awayfrom each other.

On the inside surfaces of the upper and lower halves 22a and 22b thereare integrally formed four arcuate ribs 13 and 14 respectively extendingconcentrically with the driving hole 28 at regular intervals. When thecassette cover 22 is assembled, the ribs 33 of the upper half 22a andthe ribs 34 of the lower half 22b are disposed on the samecircumference, and at the same time the ribs 33 and 34 are positionedadjacent to each other at the four corners of the cassette cover 22whereby there is formed substantially one pair of ribs at each corner.The flexible magnetic disk 21 is disposed so as to be surrounded withthese ribs 33 and 34. The ribs 33 abut the inner surface of the lowerplate 22d of the lower half 22b, and the ribs 34 abut the inner surfaceof the upper plate 22c of the upper half 22a. Accordingly, the cassettecover 2, which is flat and easy to deform even by a small externalforce, is mechanically reinforced. Furthermore, in order to avoidpossible damage or wear of the flexible magnetic disk 21, a magneticdisk protecting non-woven fabric 35 is attached by heat-weld or a likemeans between the projection 31 and the ribs 33 and also between theprojection 29 and the ribs 34 in the upper and lower halves 22a and 22b.

The distance from the center of the driving hole 28 of the lower half22b to the ribs 33 and 34 is somewhat longer than the radius of theflexible magnetic disk 21 is displaced within the cassette cover 22 bythe looseness of the center core disk 23 in the driving hole 28, theperipheral edge portion of the flexible magnetic disk 21 does not abutthe ribs 33 and 34.

In the upper and lower halves 22a and 22b of the cassette cover 22 andthe non-woven fabrics 35, there are respectively formed openings 36, 37and 38 of the same shape extending in a radial direction of the flexiblemagnetic disk 21, the openings 36, 37 and 38 being overlapped in opposedrelation. And as will be described later, a magnetic head is inserted inthe opening formed in the lower half 22b through the opening formed inthe lower non-woven fabric 35, while a head pressing pad is insertedfrom the opening 16 formed in the upper half 22a through the opening 18formed in the upper non-woven fabric 35. In FIG. 3, the referencenumerals 39a, 39b, are positioning projections for mutual engagementwhen assembling the upper and lower halves 22a and 22b.

As shown in FIG. 3, there is formed a recess 40 on each of the outersurfaces of the upper and lower halves 22a and 22b in the respectiveportions where there are formed the pad insertion opening 36 and thehead insertion opening 37. In the recess 40 there is mounted a shutter44 having a U-shaped cross-section made from aluminum, stainless steel,a synthetic resin, or the like, so as to be slidable in a predetermineddirection. In the recess 40 of the lower half 22b, as shown in FIG. 6, arectilinear guide groove 42 is formed extending along a side edgeportion of the cassette cover 22, while in relation to the guide groove42 there is formed in the shutter 41, as shown in FIG. 8, a pawl-likeprojection 43, for example, in three places, formed by inwardly bendinga part of the shutter 41 by means of pressure or the like. The pawl-likeprojection 43 of the shutter 41 is inserted in the guide groove 42 ofthe lower half 22b so that the shutter 41 is guided by the groove 22slidably in the direction of arrows A and B in FIG. 6. The shuttersliding mechanism is not limited to what has just been mentioned. Forexample, as shown in FIG. 9, a part of the shutter 41 may be subjectedto half-blanking by means of pressing or the like to form a projection44a which projects inwardly of the shutter 41, and the projection 44a isslidably fitted in the guide groove 42. Further, as shown in FIG. 10, aV-shaped projection 44b may be formed which projects inwardly of theshutter 41. This projection 44b is slidably fitted in the guide groove42. In the side edge portion of the lower half 22b where the guidegroove 42 is formed, as shown in FIG. 6 there is formed a shuttermounting and demounting recess 56 in communication with the guide groove42, for example in three places. When the shutter 41 is slid, forexample, in the direction of arrow B in FIG. 6 to the position indicatedwith a dot-dash line, the recess 56 and the pawl-like projection 43 ofthe shutter 41 become opposed to each other. In this state, if a forceis applied in a pulling direction of the shutter 41 from the cassettecover 22, the shutter 41 can be easily demounted or removed from thecassette cover 22.

In each of the opposed plate portions 41a and 41b of the shutter 41there is formed an opening 45 having substantially the same shape as thepad and head insertion openings 36 and 37. By sliding the shutter 41along the guide groove 42, the pad and the head insertion openings 36and 37 can be opened or closed selectively. In case the shutter 41 isdisposed in such a position as indicated with a solid line in FIG. 6,the opening 45 in the shutter 41 and the openings 36 and 37 in thecassette cover 22 become overlapped with one another, that is theopenings 36 and 37 are opened. On the other hand, in case the shutter 41is slid to the position shown with a dot-dash line in FIG. 4, theopenings 36 and 37 are covered and closed with the shutter 41.

In the side portion of the cassette cover 22 where the shutter 41 ismounted, there is formed a channel-shaped cutout portion 53 as shown inFIG. 3 and FIG. 6. This cutout portion 53 is opened or closed along withthe above-described sliding movement of the shutter 41. That is, whenthe opening 45 in the shutter 41, the openings 36 and 37 in the cassettecover 22, and the opening 38 of the fabric 35 overlap each other, thecut-out portion 53 is opened, while when the openings 36, 37 and 38 arecovered with the shutter 41, the cutout portion 53 is also closed. Incase the cutout portion 53 is opened, as will be described later, thecassette cover 22 can be installed up to the right position of therecording and/or reproducing apparatus, and recording and reproducingoperations can be performed. But, in case the cutout portion 53 isclosed by the shutter 41, as will be described later, the disk cassette26 canot be installed in the normal operating position on the apparatusand therefore undesired operation is prevented. In order to prevent thecassette cover 22 from being installed in an erroneous direction, thereis formed a triangular cutout portion 53 at one predetermined corner ofthe cassette cover 22.

In this embodiment, moreover, there is provided an erroneous erasepreventing mechanism at one corner of the cassette cover 22 so that theinformation recorded on the flexible magnetic disk 21 may not be erasedby mistake. That is, as shown in FIG. 3 and FIG. 11, a channel-shapedcutout portion 46 is provided at a predetermined corner of the lowerhalf 22b of the cassette cover 22, and within the cutout portion 46 anerroneous erase preventing detent 47 is connected integrally with thelower half 22b through a thin portion 49 formed by a V-shaped groove 48.On the inner surface on the tip end side (free end side) of the detent47 there is integrally formed an abutment 50 extending toward the upperplate 22c of the upper half 22a and the tip end of the abutment 50 is incontact with the inner surface of the upper plate 22c. Accordingly, evenwhen there is exerted an urging force in the direction of arrow C inFIG. 11, the erroneous erase preventing detent 47 is not separated fromthe lower half 22b. If it is desired to separate the detent 47 from thelower half 22b for the prevention of an erroneous erase, a pivotal forcemay be applied in the direction of arrow D in FIG. 11 to the tip end ofthe detent 47 whereby the thin portion 49 can be cut easily to removethe detent 47 by folding. The reason for such a construction is that inthe thin cassette cover 22 it is restricted, by thickness, to push andfold off the detent 47 inwardly. The construction as in this embodimentpermits the detent 47 to be folded off surely and easily.

At the two corner portions on the side of the opening 37 of the lowerhalf 22b and in positions outwardly deviated from the ribs 34, firstthere are formed a pair of positioning holes 51 for positioning thecassette cover 22 when the disk cassette 26 is installed onto therecording and/or reproducing apparatus. In this embodiment, moreover,auto loading cutout portions 54 and 55 have a semicircular section areformed in both side portions of the cassette cover 22. Within the cutoutportions 54 and 55 there are inserted a pair of supporting rods (notshown) of a predetermined moving mechanism for holding the cassettecover 22 and moving the latter automatically to a predetermined positionas necessary. Consequently, by utilizing the auto loading cutoutportions 54 and 55, it is possible to construct the apparatus so thatthere can be performed an automatic change of the disk cassette 26 andan automatic cassette take-out operation at the time of qualityinspection.

The following description is now provided with reference to FIG. 12 toFIG. 28 concerning the structure of the recording and/or reproducingapparatus onto which the disk cassette 26 is installed.

As shown in FIG. 12 to FIG. 14, on a chassis 61 of a recording and/orreproducing apparatus (hereinafter referred to simply as the"apparatus") 60 there are mounted four cassette receiving pins 63, 64,65 and 66 for receiving the disk cassette 26. Among these pins, on theupper ends of the two pins 63 and 64 there are integrally formedcassette positioning projections 67 and 68 respectively adapted to fitin the pair of positioning holes 51 formed in the cassette cover 22. Thecassette receiving pins 63, 64, 65 and 66 are respectively provided attheir upper ends with receiving surfaces 63a, 64a, 65a and 66a, whichare equal in height with respect to the chassis 61.

Onto the chassis 61 there are fixed a pair of L-shaped supportingmembers 69 and 70, to which a cassette pressure member 72 is attached topivots 73 and 74, respectively. The cassette pressure member 72 has aplate body 72a, and four cassette pressing pins 65, 76, 77 and 78mounted on the lower surface of the plate body 72a. That is, as shown inFIG. 15 to FIG. 17, these pins 75 to 78 are slidably supported in thevertical direction by a sleeve 79 provided in the plate body 72a and atthe same time are normally biased resiliently downwards by a compressioncoiled spring 81 interposed between the sleeve 79 and a spring shoe 80.Accordingly, the disk cassette 26 is pressed for holding toward thecassette receiving pins 63, 64, 65 and 66 by the cassette pressing pins75, 76, 77 and 78.

In this embodiment, as is apparent from FIG. 14, the disk cassette 26 isreceived at its four corners by the cassette receiving pins 63, 64, 65and 66. On the other hand, the positions wherein the cassette pressingpins 75, 76, 77 and 78 of the cassette pressure member 72 hold down thedisk cassette 26 are each deviated by a predetermined length from thepositions of the pins 63, 64, 65 and 66 toward the central side of thedisk cassette 26. That is, the cassette pressing pins 75 and 77 aredisposed nearly on a line joining the cassette receiving pins 63 and 65and are disposed between these pins 63 and 65, and are so constructed asto be in corresponding relation to the ribs 33 and 34 of the diskcassette 26. The cassette pressing pins 76 and 78 and the cassettereceiving pins 64 and 66 are disposed also in the same relation asabove.

On the chassis 61 there also is mounted a driving mechanism 82 forrotating the flexible magnetic disk 21 in the disk cassette 26. At anearly central position of the portion surrounded with the cassettereceiving pins 63, 64, 65 and 66, there is mounted a flat-type brushlessmotor 83 for rotating the flexible magnetic disk 21 in the disk cassette22. As shown in FIG. 18, on the upper surface of a rotor 83a of themotor 83, a spacer 84 is positioned in the form of a partially cutoutring-like disk along with a leaf spring member 86 to which is fixed aspring-biased driving pin 85 for positioning (centering) the flexiblemagnetic disk 21.

In the cassette cover 22, a disk-like yoke 90 having a ring-like recess88 formed in the upper surface thereof is tightened together with a pairof setscrews 91. The leaf spring member 86 is interposed between thespacer 84 and the yoke 90. The spacer 84, the leaf spring member 86, andthe yoke 90 are further tightened together with a setscrew 92, so thatthese components are rotated together with a motor shaft 83b of themotor 83.

In a nearly central part of the leaf spring member 86, as shown in FIG.18 there is formed a generally horseshoe-shaped opening 94. A pinmounting portion 96 is also integrally formed with a pair of narrowlyformed L-shaped arm positions 95, the pin mounting portion 96 beingsupported from both sides by the pair of arm portions 95. The drivingpin 85 is fixed to the pin mounting portion 96. The spring-biaseddriving pin 85, as shown in FIG. 19 to FIG. 21, is constructed of a stemportion 98 having a nearly centrally located flange 98a, a bearingportion 99 fitted and fixed over the upper end portion of the stemportion 98, and a cylindrical portion 101 mounted rotatably with respectto the stem portion 98 by means of a ball bearing 100 disposed betweenthe bearing portion 99 and the cylindrical portion 101. The stem portion98 extends through the pin mounting portion 96. On the lower end portionof the extending portion of the stem portion 98 there is fixed acylindrical mounting member 102. By the flange 98a of the stem portion98 and the mounting member 102, the pin mounting portion 96 of the leafspring member 86 is held in place whereby the spring-biased driving pin85 is secured to the pin mounting portion 96. The pin 85 is disposed insuch a state that the cylindrical portion 101 of the pin 85 has passedthrough a piercing hole 89 formed in the recess 88 of the yoke 90.Consequently, within the piercing hole 89, the pin 85 is capable ofbeing moved in the direction of arrow E in FIG. 19 by the resilience ofthe leaf spring member 86, and particularly it is pivotable in thedirection of arrows F and G centered on the arm portion 95 in FIG. 19(in other words, it is movable in the radial direction of the yoke 90).The pin 85 is mounted in such a position that the distance S₁ shown inFIG. 19 is slightly longer than the distance S₂ shown in FIG. 28.

A top portion 83c of the motor shaft 83b of the motor 83 is generallyhemispherical, and the height of the top portion 83c of the motor shaft83b is set to a predetermined level. As will be described in detaillater, in case the upper plate 22c of the cassette cover 22 warps to thelower plate 22d when installing the disk cassette 26 onto the apparatus60, the top portion 83c engages the inner surface of the upper plate 22cto correct the inward warp of the latter.

On the other hand, in the recess 88 of the yoke 90 four pairs of magnets104 are fixed with an adhesive or the like at nearly equal intervals inthe circumferential direction. On the upper surfaces of inner and outerflanges 90a, 90b of the yoke 90 there are stuck lubricant sheets 105,106 respectively consisting of a Teflon (trademark of DuPont de Nemours& Co.), sheet or the like incorporating carbon. As shown in FIG. 19 toFIG. 21, the upper surfaces of the lubricant sheets 105 and 106 (i.e.,the receiving surfaces for the center core disk 23) are positioned to beflush with each other and above the upper surfaces of the magnets 104.The cylindrical portion 101 of the pin 85 is in an upwardly projectingstate from the upper surfaces of the lubricant sheets 105 and 106.

In FIG. 12 and FIG. 13, the reference numeral 107 is a motor coverhaving an opening 107a formed in the upper surface thereof. Within theopening 107c, and the lubricant sheets 105 and 106 stuck on the yoke 90are projecting upwardly from the upper surface of the motor cover 107.

Next, an explanation will be given concerning a head moving unit in theapparatus 60.

The head moving unit includes a head support 110 onto which a magnetichead 108 is secured on a mounting plate 109, together with a feed-screw112 which is driven by a step motor 111 about the axis thereof. As shownin FIG. 12 to FIG. 14, the step motor 111 is screwed to a vertical piece113 of the chassis 61, and a motor shaft 111a of the step motor 111 isdirectly connected to the feed screw 112. The other end of the feedscrew 112 is rotatably attached to a cut-up piece 112 of the chassis 61.The feed screw 112 is disposed horizontally with respect to the chassis61.

In this embodiment, the head support 110 is constructed so as to bemovable along the axis of the feed screw 112. That is, a pair of guideshaft mounting portions 114, 115 are provided on the chassis 61, andboth end portions of a guide shaft 116 having a circular section arefixed to the mounting portions 114 and 115. The guide shaft 116, whichis disposed in parallel with the feed screw 112, extends through thehead portion 110 and in this state it is borne by a sleeve 118 fixed tothe head support 110. Consequently, the head support 110 is slidablewhile being guided by the guide shaft 116 in the direction of arrows Sand T in FIG. 12 and FIG. 24.

With the head support 110, as shown in FIG. 12 and FIG. 22, there isintegrally formed a pair of needle-like member mounting portions 120which are opposed to each other in spaced relation. The feed screw 112extends through an opening 121 formed in the vertical piece 113 of thehead support 110, and is disposed between the pair of needle-likemounting portions 120. In the upper surfaces of the pair of mountingportions 120 there are formed V-shaped grooves 122a and 122brespectively, the V-shaped grooves 122a and 122b having an inclinationcorresponding to the pitch angle of the threaded portion of the feedscrew 112 in the direction orthogonal to the axis of the feed screw 112and extending on the same straight line. A needle-like member 124 isspanned between the pair of mounting portions 120 with its end portionsinserted in the V-shaped grooves 122a and 122b. Furthermore, as shown inFIG. 24, it is inserted without looseness between and along adjacentthreads (i.e., the root) of the feed screw 112. Above the needle-likemember 124 there is disposed a keep plate 125 which is fixed onto theupper surfaces of the mounting portions 120 with a pair of setscrews 126whereby the needle-like member 124 is secured to the mounting portions120 in the aforesaid state of arrangement. Furthermore, as shown in FIG.25, a leaf spring 127 is fixed to the lower surface of one mountingportion 120 with the setscrew 126, and by virtue of a resilientrestoring force of the free end of the leaf spring 127, the feed screw112 is normally urged to the needle-like member 124 and the threadedportion of the feed screw 112 never become disengaged from each other,and the needle-like member 124 is kept engaged without looseness betweenadjacent threads.

On the head support 110, as shown in FIG. 12 and FIG. 24, there ispivotably mounted a pad supporting member 129 which holds a pad 128formed of felt or the like. More specifically, on the head support 110there are mounted a pair of opposed vertical pieces 130 extending in thedirection perpendicular to the chassis 61, and bearing 131 is fixed toeach of the vertical pieces 130 (see FIG. 12 and FIG. 13). Furthermore,pivots 132 fixed to the pad supporting member 129 are borne by thebearings 131, while between one vertical piece 130 and the head support110 there is stretched a compression coiled spring 133. Accordingly, thehead support 110 is normally urged around the pivots 132 in thedirection of arrow H in FIG. 12 and FIG. 24, namely in the direction inwhich the pad 128 comes into pressure contact with the magnetic head108. When the disk cassette 26 is not installed on the apparatus 60, thehead support 110 is urged in the direction of arrow I in FIG. 12 againstthe urging force of the compression coiled spring 133 by means of apredetermined urging mechanism such as a plunger solenoid (not shown),so that the pad 128 is spaced from the magnetic head 108. That is, thestate of the apparatus 60 shown in FIG. 12 is for the case when the diskcassette 26 is not installed or not in operation. When the disk cassette26 has been installed or in operation, the head support 110 is pivotallymoved in the direction of arrow H by virtue of the urging force of thecompression coiled spring 133. As a result, as shown in FIG. 24, themagnetic disk 21 exposed to the openings 36 and 37 in the cassette cover22 is held between the pad 128 and the magnetic head 108.

Referring now to FIG. 23, a disk 135 made of a synthetic resin or thelike is coaxially fixed onto the other end of the motor shaft 111a ofthe step motor 111, and a reflector 136 is mounted on a pair of theperipheral surface of the disk 135. On the other hand, a detector 137consisting of a light emitting element and a light receiving element(photo sensor) is disposed in opposed relation to the outer peripheralsurface of the disk 135. A rotational position of the motor shaft 111aof the step motor 111 is detected by the function of the detector 137and the reflector 136. A detection mechanism 137a for detecting amovement position of the head support 110 with respect to the feed screw112, is mounted near both ends of the feed screw 112. On the basis ofdetection signals from this detection mechanism 137a and the detector137, rotation start and stop positions of the motor shaft 111a aredetermined as will be described later. As a result, the magnetic head108 can be moved by only an amount of movement required for the magneticdisk 21 to be recorded or reproduced by the magnetic head 108 (namelywithin a predetermined range of movement). The reference numeral 138 inFIG. 12 is an optical pulse generator for detecting a rotational phaseof the flat-type brushless motor 83.

On the cassette receiving pin 65, as shown in FIG. 12 and FIG. 26, thereis mounted an erroneous erase preventing detent detecting member 140movable along the axis of the pin 65. The detecting member 140 isprovided at one end thereof with an upwardly projecting detector portion143. The detecting member 140 is normally urged upwards by a compressioncoiled spring 141 and is retained by a stopper 142 mounted on the upperend portion of the pin 65. On the other hand, a detector 144incorporating therein a light emitting element and a light receivingelement (neither shown) disposed in opposed relation to each other, isattached to the chassis 61. The detector 144 is constructed so that theother end portion of the detecting member 140 can get in between thelight emitting and receiving element along with a downward movement ofthe detecting member 140. That is, while the detecting member 140 isretained to the stopper 142 by the compression coiled spring 141, theother end portion of the detecting member 140 is spaced upwards frombetween the light emitting and receiving element. When the detectorportion 143 of the detecting member 140 has been forced down by theerroneous erase preventing detent 47 of the cassette cover 22, the otherend portion of the detecting member 140 gets in between the lightemitting and receiving elements against the urging force of thecompression coiled spring 141, whereby the recording operation isperformed in the above case. Otherwise, recording is prevented as willbe described later.

In this embodiment, in order to prevent an erroneous installation(loading) of the disk cassette 26 onto the apparatus 60, there areformed erroneous installation preventing projections 146 and 147 on thechassis 61 side in opposed relation to the channel-shaped cutout portion53 and the triangular cutout portion 52 both formed in the disk cassette26, respectively.

Next, the following description is now provided about the operation ofthe apparatus 60 having the above construction.

First, the shutter 41 of the disk cassette 26 to be installed onto theapparatus 60 is slid in the direction of arrow A in FIG. 6 until theopenings 36 and 37 of the disk cassette 26 and the opening 45 of theshutter 41 are overlapped with each other, whereby the openings 36 and37 are opened and at the same time the channel-shaped cutout portion 53of the disk cassette 26 is opened. Thereafter, the disk cassette 26 isinstalled onto the apparatus 60 by means of a cassette loadingmechanism, not shown. In this case, as shown in FIG. 14, the erroneousinstallation preventing projections 146 and 147 of the chassis 61 canget in the channel-shaped cutout portion 53 and the triangular cutoutportion 53 of the disk cassette 26, respectively, so that the cassettecover 22 can be disposed in the normal loading position, and the diskcassette 26 is placed on the cassette receiving pins 63, 64, 65 and 66by means of the cassette loading mechanism. In this case, theprojections 67 and 68 of the cassette receiving pins 63 and 64 arerespectively fitted into the positioning holes 51 and 52 formed in thecassette cover 22, whereby the positioning of the disk cassette 26 iseffected in its planar direction, i.e., longitudinal and transversedirection. At the same time, the cassette pressure member 77 movespivotally about the pivots 73 and 74 in interlock with the cassetteloading mechanism, thus allowing the pins 75, 76, 77 and 78 of thecassette pressure member 72 to force the disk cassette elasticallydownwards by virtue of the urging force of the compression coil springs81. Accordingly, the disk cassette 26 is held resiliently between thepins 63, 64, 75 and 66 and the pins 75, 76, 77 and 78 of the pressuremember 72 whereby the positioning of the disk cassette 26 in thedirection of the height is effected.

When installing the disk cassette 26, in case the cutout portion 53 iscovered with the shutter 41, or in case the triangular cutout portion 52is not disposed in the normal position (that is, in case the loadingdirection of the disk cassette 26 is not correct), since corner portionsof the shutter 41 and the disk cassette 26 will strike against theprojections 146 and 147, the disk cassette 26 is not disposed in theforegoing normal loading position. Consequently, the foregoing loadingoperation is not performed and hence recording and reproducingoperations are not carried out. It is, therefore, not possible that themagnetic head 108 will be damaged upon its abutment with the shutter 41which covers the opening 37 of the disk cassette 26.

On the other hand, the portion of the disk cassette 26 where theopenings 36 and 37 are formed is inserted between the magnetic head 108and the pad 128. For interlock during loading operation of the diskcassette 26 by means of the loading mechanism, not shown, the padsupporting member 129 is pivotally moved in the direction of arrow H inFIG. 12 and FIG. 24 by virtue of the urging force of the compressioncoiled spring 133. It thus results in that a part of the flexiblemagnetic disk 21 exposed through the opening 45 in the shutter 41, theopenings 36 and 37 in the cassette cover 22, and the opening 38 in thenon-woven fabrics 35 is held between the magnetic head 108 and the pad128.

In this case, if the erroneous erase preventing detent 47 of the diskcassette 26 has not been folded off or removed, the detector portion 143of the detecting member 140, as indicated with a dot-dash line in FIG.26, is forced down against the urging force of the compression coiledspring 141 by the detent 47, thereby allowing the gap between the lightemitting and receiving elements of the detector 144 to be interrupted.As a result, the apparatus 60 is ready to perform recording andreproducing operations on the basis of a predetermined signal from thedetector 144. On the other hand, in case the detent 47 has been foldedoff, the tip end of the detector portion 143 of the detecting member 140can get into the cutout portion 46 of the cassette cover 22. Therefore,the detecting member 140 is left to be disposed in the upper position byvirtue of the compression coiled spring 141, so that the gap between thelight emitting and receiving elements of the detector 144 is notinterrupted and hence the apparatus 60 is maintained in a state whichwill not perform a reproducing operation on the basis of a predeterminedsignal from the detector 144.

Along with such a loading operation of the disk cassette 26, the motorshaft 83b is inserted in the center aperture 24 of the center core disk23 fitted in the driving hole 28 of the lower half 22b of the diskcassette 26. In this case, if the upper plate 22c of the loaded diskcassette 26 is warped (bent) toward the lower plate 22d as indicatedwith a dot-dash line in FIG. 27, the hemispherical top 83c of the motorshaft 83b comes into contact with the nearly central part of the innersurface of the upper plate 22c by the pins 75, 76, 77 and 78. As aresult, when the loading of the disk cassette 26 is over, thedeformation (inward warp) of the upper plate 22a is already correctedand the upper plate 22a is flat, as indicated with a solid line in FIG.27.

On the other hand, when the disk cassette 26 has been installed, thepressing position of the pins 75, 76, 77 and 78 of the pressure member72 are on the diagonal lines of the pins 63, 64, 65 and 66 as previouslynoted; these positions correspond to the ribs 33 and 34 of the diskcassette 26. Therefore, if the lower plate 22d of the disk cassette 26to be installed is deformed inwardly, namely toward the upper plate 22cas indicated with a dot-dash line in FIG. 27, the lower plate 22dundergoes a force in the direction of arrows L and M through the ribs 33of the upper half 22a and the ribs 34 of the lower half 22b. It thusresults that the deformation of the lower plate 22d becomes flat asindicated with a solid line in FIG. 27.

In this embodiment, as set forth above, even if the upper and lowerplates 22c and 22d both are warped (deformed) inwardly, this warp(deformation) can be corrected to a satisfactory extent. As a result,the space within the cassette cover 22 when installed can always bemaintained constant, there is no fear of an obstacle to the rotation ofthe magnetic disk 21, and the flexible magnetic disk 21 can be rotatedwith a relatively small driving torque.

Along with the aforesaid installation (loading) of the disk cassette 26,the center core disk 23 is attracted by the magnets 104 of the yoke 90and is disposed on the lubricant sheets 105 and 106 respectively stuckon the upper surfaces of the flanges 90a and 90b of the yoke 90. In thiscase, if the position of the driving and positioning aperture 25 in thecenter core disk 23 and that of the spring-biased pin 85 are shiftedfrom each other, the pin 85 is forced down by the center core disk 23 byvirtue of the attractive force exerted between the center core disk 23and the magnets 104. As a result, as shown with a solid line in FIG. 20,the pin 85 is forced down against the resilient restoring force of theleaf spring 86, particularly the arm portion 95. In such a state, whenthe apparatus 60 is changed to the recording or reproducing mode and themotor shaft 83b of the motor 83 is rotated, the pin 85 rotates togetherwith the leaf spring 86 and the yoke 90 with respect to the center coredisk 23. At this time, the flexible magnetic disk 21 is held between themagnetic head 108 and the pad 128 as previously noted, whereby loadtorque is exerted on the magnetic disk 21. Consequently, even if africtional force is exerted between the lubricant sheets 105 and 106stuck on the yoke 90 and the center core disk 23, and between the latterand the pin 85, the center core disk 23 is not rotated and the pin 85moves around relatively to the stationary center core disk 23.Thereafter, when the driving and positioning aperture 25 in the centercore disk 23 is reached, as indicated with a dot-dash line in FIG. 28,the cyindrical portion 101 of the pin 85 gets in the aperture 25 byvirtue of the resilient restoring force of the leaf spring 86. Then, asthe motor shaft 83b rotates in the direction of arrow N, the pin 85 isfurther moved around and the cylindrical portion 101 of the pin 85 comesinto engagement first with a positioning edge a located farther from themotor shaft 83b out of a pair of longer edges of the aperture 25. Thenthe pin 85 is further moved around and comes into engagement with adriving edge 25b of the aperture 25 while the cylindrical portion 101 ofthe pin 85 is rotated with the ball bearing 100 since a holding forceinduced by the magnetic head 108 and the pad 128 and an inertia forcecaused by the difference in revolution between the yoke 90 and thecenter core disk 23, are exerted as a load torque on the magnetic disk21 and the center core disk 23. In this case, as previously noted, sincethe distance S1 shown in FIG. 19 is set slightly longer than thedistance S2 shown in FIG. 28, the pin 85 is brought into an inclinedstate by a torsional deformation of the arm portion 95 of the leafspring 86 as illustrated in FIG. 21. As a result, the axis of the pin 85now has a slight inclination with respect to the vertical direction inFIG. 21, so that on the center core disk 23 there normally is exerted anurging force in the direction of arrow P in FIG. 21 and FIG. 28 throughthe cylindrical portion 101 of the pin 85 by virtue of the resilientrestoring force of the arm portion of the leaf spring 86.

Although the load torque applied to the flexible magnetic disk 21 by themagnetic head 108 and the pad 128 is small, the provision in thisembodiment of the ball bearing 100 between the stem portion 98 and thecylindrical portion 101 allows the pin 85 to be sure to move to thepredetermined position indicated with a solid line in FIG. 28, even ifthe forming accuracy of the insertion apertures 24 and 25 in the centercore disk 23 is not very high.

As the center core disk 23 is moved in the direction of arrow P, twosides 24a and 24b of a V-shaped corner located farther from the drivingand positioning aperture 25 out of four sides of the motor shaftinsertion aperture 24 are brought into pressure contact at two pointswith the motor shaft 83b, and the center core disk 23 is positioned.Accordingly, the center of the flexible magnetic disk 21 stuck on thecenter core disk is positioned nearly on the axis of the motor shaft83b. In this state, as the motor shaft 83b rotates and the pin 85 ismoved around in the direction of arrow N in FIG. 28, the cylindricalportion 101 of the pin 85 pushes the driving edge 25b of the aperture 25so that the center core disk 23 and hence the magnetic disk 21 isrotated in the direction of arrow N. In this case, since the flexiblemagnetic disk 21 is disposed concentrically with the motor shaft 83b aspreviously noted, it is rotated in an almost centered state.

Next, an explanation is here given about the operation of the headmoving mechanism. First, when the apparatus 60 is changed, for example,to the reproducing mode in a loaded state of the disk cassette 26 in themanner as set forth hereinbefore, the flexible magnetic disk 21 rotatesin the previously described manner. Along with this rotation, a recordedinformation is read-out by the magnetic head 108 which is in slidingcontact with the recording surface of the flexible magnetic disk 21, anda synchronizing signal contained in the read-out information is suppliedto a step motor driving circuit (not shown). Every time such asynchronizing signal is supplied, a predetermined driving current isprovided from the above driving circuit to the step motor 111, wherebythe motor shaft 111a is rotated in the direction of arrow Q (shown inFIG. 12 and FIG. 24) in steps by a predetermined rotational c angle(e.g., 15°). Along with this rotation of the motor shaft 111a, theneedle-like member 124 inserted without looseness between adjacentthreads of the feed screw 112 is moved in the direction of arrows S bythe feed screw 112. Thereby the head support 110, together with theneedle-like member 124 is guided by the guide shaft 116 and movesstepwise to the next circular recording track intermittently, namely atevery rotation of flexible magnetic disk head 108 and the pad supportingmember 129 both mounted on the head support 110 slide integrally witheach other and with the flexible magnetic disk 21 held therebetween, andmove intermittently in the longitudinal direction within the head andpad insertion openings 36 and 37 in the disk cassette, namely along aradial direction of the flexible magnetic disk 21.

In this embodiment, as the pitch of the feed screw 112 is relativelysmall and the step motor 111 has a relatively large rotational angle(e.g., about 15°) per one step, even if the recording track pitch on theflexible magnetic disk 21 is small, it is possible to effect positioningof the magnetic head 108 with high accuracy with respect to therecording track to be reproduced. This is because even if step motorshave the same mechanical accuracy in a single step rotation, the ratioof this mechanical accuracy to the one step rotational angle is smallerin a step motor having a wider rotational angle, and therefore, themagnetic head 108 can be moved with high accuracy.

During the above movement, the feed screw 112 undergoes a downward forcein FIG. 24 and FIG. 25 through the needle-like member 124. But since anurging force toward the needle-like member 124 is exerted at all timeson the feed screw 112 by means of the leaf spring 127, the threads ofthe feed screw 112 and the needle-like member 124 will never becomedisengaged.

In this way, the magnetic head 108 in sliding contact with the flexiblemagnetic disk 21 moves stepwise and radially from the outer peripheralside toward the center of the magnetic disk 21 at every rotation of themotor shaft 83b, namely every time there is fed a synchronizing signalrecorded on each circular recording track. When the head support 110 hasbeen moved to a predetermined position and the magnetic head 108 hasreached near the inside terminal edge portion of the magnetic surface ofthe flexible magnetic disk 21, the position of the head support 110 isdetected by a detection mechanism 117a. Then, when the detector 137 andthe reflector 136 have become opposed to each other along with therotation of the motor shaft 111a of the step motor 111, the rotation ofthe motor shaft 111a in the direction of arrow N is stopped on the axisof detection signals from the above detection mechanism 117a and thedetector 137. Conversely, in case the feed screw 112 has been rotated inthe direction of arrow R in FIG. 12 and FIG. 24 by means of the stepmotor 111, the magnetic head 108 is moved from the radially central sideof the flexible magnetic disk 21 toward the outer peripheral side (inthe direction of arrow T in FIG. 12 and FIG. 24). And when it hasreached the outside terminal edge portion of the magnetic surface, therotation of the motor shaft 111a in the direction opposite to theprevious arrow N direction is stopped.

Along with the above operation, the information recorded on therecording surface of the flexible magnetic disk 21 is reproduced. Also,in the recording operation, the same operation is performed as set forthhereinbefore.

According to the flexible magnetic disk cassette 26 having the aboveconstruction, the center core disk 23 is formed in the shape of a pan,and the center hollow 23a of the center core disk 23 and the projection30 of the upper half 22a are held in a fitted state, so that even if theflexible magnetic disk 21 is displaced toward the lower half 22b due toits own weight while the disk cassette 26 is not in use, the movement ofthe center core disk 23 and hence of the magnetic disk 21 in theirplanar direction is surely restricted within a predetermined range bythe engagement between the center core disk 23 and the projection 30.Consequently, it is possible to eliminate the risk that the peripheraledge portion of the flexible magnetic disk 21 might come into contactwith the ribs 33 and 34 and be damaged thereby. Particularly in the caseof a flat-type disk cassette, it is preferable that the movable range inthe vertical direction of the center core disk 23 is as large aspossible in consideration of dimensional variations of variouscomponents. In this connection, by forming the center core disk 23 inthe shape of a pan as in the present embodiment, it becomes possible toaccept a larger movable range than in the case of such a plate-likecenter core disk 6 as shown in FIG. 27.

Moreover, as previously noted, even if the upper plate 22c and the lowerplate 22d of the cassette cover 22 are deformed to a certain extent inthe direction away from each other because of a low mechanical strengthof the cassette cover 22, the movable range of the center core disk 23can be surely restricted. Besides, since the center core disk 23 isconstructed of a thin plate, it is possible to reduce its weight ascompared with a conventional plate-like center core disk, and this inturn permits the use of a small-sized low torque motor as the drivingsource for the magnetic disk 21.

Furthermore, when joining together the flexible magnetic disk 21 and thecenter core disk 23, the convexed portion 23b of the center core disk 23serves as a guide allowing the magnetic disk 21 to be mounted with veryhigh accuracy with respect to the center core disk 23. Consequently, thevibration of the outer part of the flexible magnetic disk 21 duringrotation can be kept to a minimum.

Furthermore, the distance from the yoke 90 to the inner surface of theupper plate 22c of the upper half 22d at the time of installation of thedisk cassette 26 can be relatively long. This permits the formation of ahemispherical tapered portion at the top 83c of the motor shaft 83b. Asa result, even without forming an opening in the upper plate 22c incorresponding relation to the motor shaft 83b, the center core disk 23can be fully guided by the tapered portion.

An embodiment of this invention has been described above, but theinvention is not limited thereto and various modifications may be madeon the basis of the technical concept of this invention.

For example, the material of the center core disk 23 is not limited toiron, and any magnetic material may be used. Furthermore, the centercore disk 23 may be formed of a hard material incorporating a magneticpowder. Regarding the dimensional relation between the upper and lowerhalves 22a and 22b of the cassette cover 22 and the center core disk 23,the values of L₁ and L₁₂ previously shown are merely an example, whichmay be changed if only there exists an overlapping portion between theprojection 30 of the upper half 22a and the lower half 22b. It is alsopossible to form the projection 30 on the lower half 22b so as toproject to the upper half 22a and to insert it in the center hollow 23aof the center core disk 23.

Although the illustrative embodiments of the invention have beendescribed in detail herein with reference to the accompanying drawings,it is to be understood that the invention is not limited to the preciseembodiments, and that various changes and modifications can be effectedtherein by one skilled in the art without departing from the scope andspirit to the invention as defined in the appended claims.

I claim as my invention:
 1. A flexible magnetic disk cassettecomprising:(a) a flexible magnetic disk; (b) a center core disk.[.having a.]. .Iadd.including an upwardly opening, pan-shaped.Iaddend.center hollow .[.and.]. .Iadd.having a circular peripheral wallfrom which a .Iaddend.raised fringe .Iadd.extends radiallyoutward.Iaddend., and being attached at a center of said flexiblemagnetic disk with said raised fringe; and (c) a cover .[.having.]..Iadd.including .Iaddend.an upper half and .Iadd.a .Iaddend.lower half.[.containing.]. .Iadd.having confronting inner surfaces between which.Iaddend.said flexible magnetic disk .[.with.]. .Iadd.and .Iaddend.saidcenter core disk .Iadd.are contained.Iaddend., said lower half having adriving hole .[.a little.]. .Iadd.diametrically .Iaddend.larger than anouter diameter of said .Iadd.circular peripheral wall of the.Iaddend.center hollow of said center core disk and .Iadd.being radiallyengageable at an edge of said driving hole with said circular peripheralwall for locating said magnetic disk within said cover, and said upperhalf having a ring-shaped projection extending therefrom toward saidinner surface of the lower half and said driving hole, said ring-shapedprojection having an outer diameter smaller than an inner diameter ofsaid circular peripheral wall of said upwardly opening center hollow andbeing radially engageable with said circular peripheral wall forlocating said magnetic disk within said cover, said circular peripheralwall of the center hollow extending into said driving hole or saidprojection extending into said center hollow radially inside saidcircular peripheral wall in all positions of said magnetic disk andcenter core disk between said upper and lower halves of thecover..Iaddend. .[.2. A flexible magnetic disk cassette as claimed inclaim 1; wherein said upper half of said cover is provided with aring-shaped projection having a diameter a little smaller than an innerdiameter of said center hollow of the center core disk..]. .[.3. Aflexible magnetic disk cassette as claimed in claim 2; wherein saidraised fringe and said ring-shaped projection are so designed as toprevent said flexible magnetic disk from undesirable positioning withinsaid cover when said flexible magnetic disk is not ready for use..]. 4.A flexible magnetic disk cassette comprising:(a) a flexible magneticdisk; (b) a pan-shaped one-piece center core disk of magnetic material.[.having a.]. .Iadd.including an upwardly opening .Iaddend.centerhollow .[.and.]. .Iadd.having a circular peripheral wall from which a.Iaddend.raised fringe .Iadd.extends radially outward.Iaddend., saidcenter core disk being attached at a center of said flexible magneticdisk by said raised fringe; and (c) a cassette cover .[.having.]..Iadd.including .Iaddend.an upper half and .Iadd.a .Iaddend.lower half.[.containing.]. .Iadd.having confronting inner surfaces between which.Iaddend.said flexible magnetic disk .[.with.]. .Iadd.and .Iaddend.saidcenter core disk .Iadd.are contained.Iaddend., said lower half having adriving aperture .Iadd.diametrically .Iaddend.larger than an outerdiameter of said .Iadd.circular peripheral wall of the .Iaddend.centerhollow of said center core disk .Iadd.and being radially engageable atan edge of said driving aperture with said circular peripheral wall forlocating said magnetic disk within said cover, and said upper halfhaving a ring-shaped projection extending therefrom toward said innersurface of the lower half and said driving aperture, said ring-shapedprojection having an outer diameter smaller than an inner diameter ofsaid circular peripheral wall of the upwardly opening center hollow andbeing radially engageable with said circular peripheral wall forlocating said magnetic disk within said cover, said circular peripheralwall of the center hollow extending into said driving aperture or saidprojection extending into said center hollow radially inside saidcircular peripheral wall in all positions of said magnetic disk andcenter core disk between said upper and lower halves of saidcover..Iaddend.
 5. A magnetic disk cassette comprising:a flexiblemagnetic disk; a center core disk attached and positioned in an apertureat a center of the flexible magnetic disk; the center core disk.[.having.]. .Iadd.being pan-shaped and including .Iaddend.an.Iadd.upwardly opening .Iaddend.annular center hollow .Iadd.having acircular peripheral wall .Iaddend., and a cover .[.having.]..Iadd.including .Iaddend.an upper wall and .Iadd.a .Iaddend.lower wall.Iadd.having confronting inner surfaces .Iaddend.between which theflexible magnetic disk is positioned, the upper wall having a ring-likeprojection .[.receivable.]. .Iadd.received .Iaddend.in the annularhollow of the center core disk when the magnetic disk is assembled inthe cover .Iadd.and being radially engageable with said circularperipheral wall of said annular hollow for locating said magnetic diskwithin said cover.Iaddend., the lower wall having a driving hole foraccess to the center core disk by a driving mechanism.Iadd., thecircular peripheral wall of said annular hollow extending into thedriving hole and being radially engageable with said driving hole at anedge thereof for locating said magnetic disk within said cover, and saidprojection extending from the upper wall toward the inner surface of thelower wall and said driving hole, said circular peripheral wall of theannular hollow extending into said driving hole or said projectionextending into said annular hollow radially inside said circularperipheral wall in all positions of said magnetic disk and center coredisk between said upper and lower walls of said cover..Iaddend. .[.6. Acassette according to claim 5 wherein the center core disk at leastpartially extends into the driving hole, the driving hole having adiameter slightly larger than an outer diameter of the annular hollow ofthe center core disk..].
 7. A magnetic disk cassette, comprising:aflexible magnetic disk; a .Iadd.pan-shaped .Iaddend.center core disk.[.having a.]. .Iadd.including an upwardly opening .Iaddend.centerhollow .[.and.]. .Iadd.having a circular peripheral wall from which.Iaddend.a ring-like raised fringe .Iadd.extends radiallyoutward.Iaddend., said raised fringe providing an attachment surfacemeans which together with an adhesive attachs the center core disk tothe flexible magnetic disk in a central aperture thereof; and a cover.[.having.]. .Iadd.including .Iaddend.an upper wall and .Iadd.a.Iaddend.lower wall .[.containing the .]. .Iadd.having confronting innersurfaces between which said .Iaddend.flexible magnetic disk .[.with.]..Iadd.and .Iaddend.the center core disk .Iadd.are contained.Iaddend.,the lower wall having a driving hole positioned for permitting access todrive the center core disk from an external driving means.Iadd., saiddriving hole being diametrically larger than an outer diameter of saidcircular peripheral wall of the center hollow of said center core diskand being radially engageable at an edge of said driving hole with saidcircular pripheral wall for locating said magnetic disk within saidcover, and said upper wall having a ring-shaped projection extendingtherefrom toward said inner surface of the lower wall and said drivinghole, said projection having an outer diameter smaller than an innerdiameter of said circular peripheral wall of the upwardly opening centerhollow and being radially engageable with said circular peripheral wallfor locating the magnetic disk within said cover, said circularperipheral wall of the center hollow extending into said driving holeand said projection extending into said center hollow radially insidesaid circular peripheral wall in all positions of said magnetic disk andcenter core disk between said upper and lower walls of saidcover..Iaddend.
 8. A magnetic disk cassette, comprising:a flexiblemagnetic disk; a pan-shaped center core disk .[.having a.]..Iadd.including an upwardly opening .Iaddend.center hollow .[.and.]..Iadd.having a circular peripheral wall from which a .Iaddend.raisedfringe .Iadd.extends radially outward .Iaddend.and being attached to acenter of said flexible magnetic disk with said raised fringe; a cover.[.having.]. .Iadd.including .Iaddend.an upper half and .Iadd.a.Iaddend.lower half .[.containing.]. .Iadd.having confronting innersurfaces between which .Iaddend.said flexible magnetic disk .[.with.]..Iadd.and .Iaddend.said center core disk .Iadd.are contained.Iaddend.,said lower half having a driving hole for access by a driving means tothe center core disk; .Iadd.said upper half having a ring-shapedprojection extending therefrom toward said inner surface of the lowerhalf and said driving hole, said driving hole being diametrically largerthan an outer diameter of said circular peripheral wall of the centerhollow of said center core disk and being radially engageable at an edgeof said driving hole with said circular peripheral wall for locatingsaid magnetic disk within said cover, said ring-shaped projection havingan outer diameter smaller than an inner diameter of said circularperipheral wall of the upwardly opening center hollow and being radiallyengageable with said circular peripheral wall for locating said magneticdisk within said cover, said circular peripheral wall of the centerhollow extending into said driving hole or said projection extendinginto said center hollow radially inside said circular peripheral wall inall positions of said magnetic disk and center core disk between saidupper and lower halves of said cover;.Iaddend. first and seconddisk-like cleaning fabrics positioned between the magnetic disk and therespective upper and lower .[.walls.]. .Iadd.halves.Iaddend.; and theupper and lower .[.walls.]. .Iadd.halves .Iaddend.and the first andsecond cleaning fabrics having a magnetic head opening means therein topermit access to a recording surface of the magnetic disk by a magnetichead.
 9. A flexible magnetic disk cassette system, comprising:a cassetteformed of a flexible magnetic disk having a pan-shaped center core diskforming .[.a.]. .Iadd.an upwardly opening .Iaddend.center hollow.[.and.]. .Iadd.surrounded by an .Iaddend.outer convex portion andhaving a raised .[.flange.]. .Iadd.fringe .Iaddend.upwardly of a lowersurface of the center core disk .Iadd.and extending radially outwardfrom said outer convex portion.Iaddend., the center core disk beingattached at a center of the flexible magnetic disk with said raisedfringe, and a cover .[.having.]. .Iadd.including .Iaddend.an upper walland a lower wall .[.containing.]. .Iadd.having confronting innersurfaces between which .Iaddend.the flexible magnetic disk .Iadd.iscontained, .Iaddend.the lower wall having a driving hole.Iadd.diametrically larger than an outer diameter of said outer convexportion and being radially engageable at an edge of said driving holewith said outer convex portion for locating said magnetic disk withinsaid cover, said driving hole being .Iaddend.aligned with the centercore disk, said center core disk having a central positioning apertureand an offset driving aperture; .Iadd.said upper wall having aring-shaped projection extending therefrom toward said inner surface ofthe lower wall and said driving hole, said ring-shaped projection havingan outer diameter smaller than an inner diameter of said outer convexportion surrounding the upwardly opening center hollow and beingradially engageable with said outer convex portion for locating saidmagnetic disk within said cover, said outer convex portion extendinginto said driving hole or said projection extending into said centerhollow radially inside said outer convex portion in all positions ofsaid magnetic disk and center core disk between said upper and lowerhalves of the cover; .Iaddend.and .[.a.]. driving andrecording/reproducing system means for receiving the cassette, saidsystem means having driving means engageable with the center core disk..[.10. A system according to claim 9; wherein a ring-like projectionextends from an inside surface of the upper wall of the cassette coverand is engageable in a center hollow of the center core disk..].
 11. Aflexible magnetic disk cassette driving apparatus for rotating aflexible magnetic disk having a center core and positioned within.[.the.]. .Iadd.a .Iaddend.cassette .Iadd.housing having upper and lowerwalls between which said disk is contained.Iaddend., comprising:drivingmeans coupled with the center core of the flexible magnetic disk forrotating it at a predetermined speed; cassette supporting means mountedon a chassis for receiving and .[.positioning.]. .Iadd.supporting.Iaddend.said .[.flexible magnetic disk.]. cassette .Iadd.housing atsaid lower wall; .Iaddend. cassette pressing means .Iadd.bearing againstsaid upper wall .Iaddend.for depressing said cassette .Iadd.housing.Iaddend.on said cassette supporting means; and .[.positioning.]. meanson said driving means for .[.positioning.]. .Iadd.engaging .Iaddend.aninner surface of .[.an.]. .Iadd.said .Iaddend.upper wall of said diskcassette .Iadd.housing and positioning said upper wall in asubstantially flat plane relative to an inner surface of said lower wallthereof..Iaddend.
 12. The driving apparatus of claim 11 wherein thecassette supporting means comprises a plurality of spring biased memberspressing down on the upper wall of the cassette at outer regionsthereof.
 13. A driving apparatus according to claim 11 wherein said.[.positioning.]. means for .[.positioning.]. .Iadd.engaging.Iaddend.the inner surface of the upper wall of the disk cassette.Iadd.housing .Iaddend.comprises an end .Iadd.surface .Iaddend.of acenter positioning pin positioned within a central aperture of thecentral core.Iadd., said end surface being positioned in saidplane..Iaddend.
 14. The apparatus of claim 13 wherein the centerpositioning pin has a hemispherical top surface.
 15. A flexible magneticdisk cassette system comprising:a disk cassette formed of a flexiblemagnetic disk positioned within a cover having upper and lower wallsclosely spaced to the flexible magnetic disk, said flexible magneticdisk having a central aperture with a corresponding aperture in thelower wall of the disk cassette; a drive mechanism for receiving thedisk cassette thereon and having a pin associated therewith which ispositioned through the aperture of the lower wall of the cassette andthrough the aperture of the magnetic disk; and an end of the pinabutting against an inner surface of the upper wall of the cassette whenthe cassette is in position on the driving apparatus so as to insure agiven position of the upper wall relative to the lower wall so as toprevent any undesired warping contact of the inner surfaces of the upperand lower walls with the flexible magnetic disk.
 16. A system accordingto claim 14 wherein biasing means are provided so as to press downwardlyat outer peripheral edges of the cassette when it is in position on thedriving apparatus.
 17. The system of claim 16 wherein structuralelements are provided in the cassette disk such that when the outerperipheral biasing members are pressing down and the center pin pressesup at the inner surface of the upper wall, the upper wall becomessubstantially flat and the lower wall becomes substantially flat so asto prevent any warping contact between the upper and lower walls and theflexible magnetic disk.
 18. A magnetic disk cassette, comprising:aflexible magnetic disk; a cover .[.having.]. .Iadd.including.Iaddend.upper and lower walls .Iadd.having confronting inner surfaces.Iaddend.between which the flexible magnetic disk is positioned, saidlower wall having a driving hole .[.means.]. therein through which theflexible disk .[.may be.]. .Iadd.is .Iaddend.driven; a pan-shapedcenter-core disk having magnetic material therein and forming .[.a.]..Iadd.an upwardly opening .Iaddend.center hollow .[.and.]..Iadd.surrounded by an .Iaddend.outer convex portion at a centralportion of the magnetic disk and having in a lower surface of thepan-shaped disk a center aperture .[.means.]. for receiving a centerpositioning pin and a driving aperture .[.means.]. for receiving a.Iadd.spring biased .Iaddend.driving pin of .[.said.]. .Iadd.a.Iaddend.drive device; .Iadd.said upper wall having a ring-shapedprojection extending therefrom toward said inner surface of the lowerwall and said driving hole, both said driving hole at an edge thereofand said projection being radially engageable with said outer convexportion for locating said magnetic disk within said cover, said centerhollow extending into said driving hole or said projection extendinginto said center hollow radially inside said outer convex portion in allpositions of said magnetic disk between said upper and lower walls ofthe cover; .Iaddend.and the center aperture .[.means.]. being.[.slightly.]. offset from a center point of the flexible magnetic diskand being .[.designed slightly.]. larger than the center positioning pinsuch that when the spring biased driving pin engages an edge of thedriving aperture .[.means.]. the center positioning pin of the drivedevice abuts against an edge of the center aperture .[.means.]. and acentral axis of the center positioning pin will lie on the center pointof the magnetic disk.
 19. A .[.magnetic.]. .Iadd.flexible .Iaddend.diskcassette .Iadd.for use in a magnetic recording and reproducingapparatus.Iaddend., comprising:a flexible disk; a cover .[.having.]..Iadd.including .Iaddend.upper and lower walls .Iadd.having confrontinginner surfaces .Iaddend.between which the flexible disk is positioned,said lower wall having a driving hole .[.means.]. therein through whichthe flexible disk .[.may be.]. .Iadd.is .Iaddend.driven .Iadd.and saidupper wall having a ring-like projection extending therefrom toward saidinner surface of said lower wall and said driving hole; and .Iaddend. apan-shaped center-core disk of magnetic material .[.is.]. positionedcentrally on the .[.magnetic.]. .Iadd.flexible .Iaddend.disk and.[.has.]. .Iadd.having .Iaddend.an outer convex portion .Iadd.at acentral portion .Iaddend.receivable in and .Iadd.of .Iaddend.a diameter.[.slightly.]. smaller than .Iadd.an inner diameter of .Iaddend.saiddriving hole .[.means.]. in the lower wall and .[.a.]. .Iadd.an upwardlyopening .Iaddend.center hollow having an inner diameter .[.slightly.].larger than .[.a.]. .Iadd.an outer .Iaddend.diameter of .[.a.]..Iadd.said ep projection from said upper wall .[.receivable within saidcenter hollow.]..Iadd., both said driving hole at an edge thereof andsaid projection being radially engageable with said outer convex portionfor locating said flexible disk within said cover, said outer convexportion extending into said driving hole or said projection extendinginto said center hollow radially inside said outer convex portion in allpositions of said flexible disk and center-core disk between said upperand lower walls of said cover.
 20. A .Iadd.flexible disk.Iaddend.cassette according to claim 19 wherein the pan-shapedcenter-core disk constructed of magnetic material is mounted on acentral aperture of the flexible .[.magnetic.]. disk.
 21. A.Iadd.flexible disk .Iaddend.cassette according to claim 19 wherein thecenter-core disk has a raised fringe at which it is attached to theflexible .[.magnetic.]. disk.
 22. A .[.magnetic.]. .Iadd.flexible.Iaddend.disk cassette according to claim 19 wherein the projection atthe upper wall is circular and in the form of an annular ring.
 23. A.[.magnetic.]. .Iadd.flexible .Iaddend.disk cassette .Iadd.for use in amagnetic recording and reproducing apparatus.Iaddend., comprising:aflexible disk; a cover .[.having.]. .Iadd.including .Iaddend.upper andlower walls .Iadd.having confronting inner surfaces .Iaddend.betweenwhich the flexible disk is positioned, said lower wall having a drivinghole .[.means.]. therein through which the flexible disk .[.may be.]..Iadd.is .Iaddend.driven .Iadd.and said upper wall having a ring-likeprojection extending therefrom toward said inner surface of said lowerwall and said driving hole.Iaddend.; and a pan-shaped center-core disk.[.having a.]. .Iadd.including an upwardly opening .Iaddend.hollowcentral portion .Iadd.having a circular peripheral wall .Iaddend.whichreceives .[.a.]. .Iadd.said .Iaddend.projection from said upper wall,said pan-shaped center-core disk being provided at a central portion ofthe .[.magnetic.]. .Iadd.flexible .Iaddend.disk.Iadd.; both said drivinghole at an edge thereof and said projection being radially engageablewith said circular peripheral wall for locating said flexible diskwithin said cover; said circular peripheral wall of the portionextending into said driving hole or said projection extending into saidhollow central portion radially inside said circular peripheral wall inall positions of said flexible disk and said center-core disk betweensaid upper and lower walls of said cover. .Iaddend.
 24. A cassetteaccording to claim 23 wherein the pan-shaped center-core disk is of amagnetic material, has a raised fringe relative to a lower surface, andthe .[.magnetic.]. .Iadd.flexible .Iaddend.disk has an aperture withinwhich the pan-shaped center-core disk is positioned .[.therein.]., andthe .[.magnetic.]. .Iadd.flexible .Iaddend.disk .[.attaching.]. .Iadd.isattached .Iaddend.to the center-core disk at said fringe by adhesive..Iadd.25. A cassette according to claim 24; wherein said flexible diskis magnetic..Iaddend. .Iadd.26. A cassette according to claim 24;wherein said projection from the upper wall is circular and in the formof an annular ring having an outer diameter slightly smaller than aninner diameter of said hollow central portion..Iaddend. .Iadd.27. Aflexible disk cassette according to claim 19; wherein said flexible diskis magnetic..Iaddend.